A device of this type is known, for example, from U.S. Pat. No. 5,702,489 A.
In order to fasten a prosthesis system securely to an amputation stump of a patient, negative pressure is frequently generated between the amputation stump or a liner pulled over the same, for example produced from an elastomer, and the prosthesis shaft. Between the prosthesis shaft and the liner, which is pulled over an amputation stump, there is generated an inner volume which it is necessary to evacuate. As a rule, the prosthesis shaft has a distal through-bore for this purpose to which a vacuum pump is connected. An arrangement of this type is known, for example, from WO 2006/135851 A2. In this case, the vacuum pump together with a power supply provided for it is part of the prosthesis structure. A switch by means of which the vacuum pump can be activated is arranged on the prosthesis structure itself such that the wearer of the prosthesis system is himself able to set the negative pressure which is acceptable to him and is necessary so that the prosthesis system sits in a fixed manner.
If a prosthesis system of this type is worn over a longer period, for example a day, it is possible for air to penetrate into the inner volume between the liner and the prosthesis shaft as a result of the movement of the amputation stump and of the prosthesis system as well as a result of small leakages. This causes the negative pressure to decrease, as a result of which the fastening of the prosthesis system to the amputation stump is weakened.
The advantage of the embodiment provided in WO 2006/135851 A2 is that the wearer of the prosthesis system always carries the vacuum pump on him as it is part of the prosthesis system. If, as a result of penetrated air, the adhesive effect of the prosthesis system were to be reduced, the wearer can simply activate the vacuum pump by means of the switch and thus re-establish the optimum pressure. If the pressure is measured by means of a sensor, the pump can also be automatically activated. However, a disadvantage of the embodiment shown is that, on the one hand, a sufficient power supply, for example provided by batteries, always has to be provided for the vacuum pump and, on the other hand, both the weight of said power supply and that of the vacuum pump have to be taken along. In addition, it is possible, in particular in the case of short prosthesis systems, for there not to be enough space on the prosthesis system itself to accommodate the vacuum pump and its power supply in the most unobtrusive manner possible.
Consequently, the provision of an external vacuum pump is known, for example from U.S. Pat. No. 5,702,489 and U.S. Pat. No. 6,926,742.
In U.S. Pat. No. 5,702,489 an adapter element is arranged between the prosthesis shaft and the remaining prosthesis structure for this purpose. Said adapter element has a channel, the one orifice of which is connected to the through-bore which is provided in the prosthesis shaft. A connecting device to which, for example, the pump is connected, is provided at the other end of the channel which exits laterally out of the adapter element. A needle valve, by means of which the channel can be closed when no pump is connected to the second output, is provided in between.
A disadvantage of said system is that the wearer of the prosthesis system can only equalize a possible loss of pressure between the liner and the prosthesis shaft if he brings along with him a vacuum pump as a separate tool. In addition, he then has to connect said vacuum pump to the corresponding device of the prosthesis system or of the adapter element, which is difficult to impossible in particular for older or mobility-challenged wearers of prosthesis systems. In addition, the valve which closes the second orifice of the channel when no pump is connected can be opened even without a connected vacuum pump. In this case, air penetrates through the channel into the inner volume such that the prosthesis no longer adheres to the amputation stump.
At least to remedy said last disadvantage, WO 2010/036370 A1 proposes providing at one end of the channel a non-return valve which reliably prevents ingress of air into the inner volume. If a negative pressure pump is connected to the second orifice of the channel, air can nevertheless be pumped out of the inner volume as the non-return valve enables through-flow in said direction. The advantage of said arrangement where air is not able to ingress into the inner volume is at the same time its disadvantage. In particular when the wearer of the prosthesis system wants to put the prosthesis down, it is advantageous to refill the inner volume with air. This is not possible in the case of the embodiment shown there as the non-return valve prevents this in a secure manner. In addition, the disadvantage of a fixed non-return valve is that the opening pressure of the valve falsifies the measuring of the negative pressure. With a return flow through the pump, the control system registers a drop in negative pressure which is, however, not present in the shaft.